Phytoplankton

Phytoplankton/ˌfaɪtoʊˈplæŋktən/ are the autotrophic (self-feeding) components of the plankton community and a key part of oceans, seas and freshwater basin ecosystems. The name comes from the Greek words φυτόν (phyton), meaning "plant", and πλαγκτός (planktos), meaning "wanderer" or "drifter".[1] Most phytoplankton are too small to be individually seen with the unaided eye. However, when present in high enough numbers, some varieties may be noticeable as colored patches on the water surface due to the presence of chlorophyll within their cells and accessory pigments (such as phycobiliproteins or xanthophylls) in some species.

Phytoplankton absorb energy from the Sun and nutrients from the water to produce their own food. In the process of photosynthesis, phytoplankton release molecular oxygen (O2) into the water. It is estimated that between 50% and 85% of the world's oxygen is produced via phytoplankton photosynthesis.[7][8][9][10][11] The rest is produced via photosynthesis on land by plants.[9] Furthermore, phytoplankton photosynthesis has controlled the atmospheric CO2/O2 balance since the early Precambrian Eon.[12] (See Biological pump.)

The effects of anthropogenic warming on the global population of phytoplankton is an area of active research. Changes in the vertical stratification of the water column, the rate of temperature-dependent biological reactions, and the atmospheric supply of nutrients are expected to have important effects on future phytoplankton productivity.[16][17]

The effects of anthropogenic ocean acidification on phytoplankton growth and community structure has also received considerable attention. Phytoplankton such as coccolithophores contain calcium carbonate cell walls that are sensitive to ocean acidification. Because of their short generation times, evidence suggests some phytoplankton can adapt to changes in pH induced by increased carbon dioxide on rapid time-scales (months to years)[18][19].

Phytoplankton serve as the base of the aquatic food web, providing an essential ecological function for all aquatic life. Under future conditions of anthropogenic warming and ocean acidification, changes in phytoplankton mortality may be significant.[citation needed][further explanation needed] One remarkable Of the many food chains in the ocean – remarkable due to the small number of links – is that of phytoplankton sustaining krill (a crustacean similar to a tiny shrimp), which in turn sustain baleen whales.

In the early twentieth century, Alfred C. Redfield found the similarity of the phytoplankton’s elemental composition to the major dissolved nutrients in the deep ocean.[25] Redfield proposed that the ratio of carbon to nitrogen to phosphorus (106:16:1) in the ocean was controlled by the phytoplankton’s requirements, as phytoplankton subsequently release nitrogen and phosphorus as they are remineralized. This so-called “Redfield ratio” in describing stoichiometry of phytoplankton and seawater has become a fundamental principle to understand marine ecology, biogeochemistry and phytoplankton evolution.[26] However, the Redfield ratio is not a universal value and it may diverge due to the changes in exogenous nutrient delivery[27] and microbial metabolisms in the ocean, such as nitrogen fixation, denitrification and anammox.

The dynamic stoichiometry shown in unicellular algae reflects their capability to store nutrients in an internal pool, shift between enzymes with various nutrient requirements and alter osmolyte composition.[28][29] Different cellular components have their own unique stoichiometry characteristics,[26] for instance, resource (light or nutrients) acquisition machinery such as proteins and chlorophyll contain a high concentration of nitrogen but low in phosphorus. Meanwhile, growth machinery such as ribosomal RNA contains high nitrogen and phosphorus concentrations.

Based on allocation of resources, phytoplankton is classified into three different growth strategies, namely survivalist, bloomer[30] and generalist. Survivalist phytoplankton has a high ratio of N:P (>30) and contains an abundance of resource-acquisition machinery to sustain growth under scarce resources. Bloomer phytoplankton has a low N:P ratio (<10), contains a high proportion of growth machinery, and is adapted to exponential growth. Generalist phytoplankton has similar N:P to the Redfield ratio and contain relatively equal resource-acquisition and growth machinery.

A 2010 study published in Nature reported that marine phytoplankton had declined substantially in the world's oceans over the past century. Phytoplankton concentrations in surface waters were estimated to have decreased by about 40% since 1950, at a rate of around 1% per year, possibly in response to ocean warming.[31][32] The study generated debate among scientists and led to several communications and criticisms, also published in Nature.[33][34][34][35] In a 2014 follow-up study, the authors used a larger database of measurements and revised their analysis methods to account for several of the published criticisms, but ultimately reached similar conclusions to the original Nature study.[36] These studies and the need to understand the phytoplankon in the ocean led to the creation of the Secchi Disk Citizen Science study in 2013.[37] The Secchi Disk study is a global study of phytoplankton conducted by seafarers (sailors, anglers, divers) involving a Secchi Disk and a smartphone app.

Estimates of oceanic phytoplankton change are highly variable. One global ocean primary productivity study found a net increase in phytoplankton, as judged from measured chlorophyll, when comparing observations in 1998–2002 to those conducted during a prior mission in 1979–1986.[38] Chlorophyll are photosynthetic pigments that are often used as an indicator of phytoplankton biomass. However, using the same database of measurements, other studies concluded that both chlorophyll and primary production had declined over this same time interval.[39][40] The airborne fraction of CO2 from human emissions, the percentage neither sequestered by photosynthetic life on land and sea nor absorbed in the oceans abiotically, has been almost constant over the past century, and that suggests a moderate upper limit on how much a component of the carbon cycle as large as phytoplankton have declined.[41] In the northeast Atlantic, where a relatively long chlorophyll data series is available, and the site of the Continuous Plankton Recorder (CPR) survey, a net increase was found from 1948 to 2002.[42] During 1998–2005, global ocean net primary productivity rose in 1998, followed by a decline during the rest of that period, yielding a small net increase.[43] Using six climate model simulations, a large multi-university study of ocean ecosystems predicted "a global increase in primary production of 0.7% at the low end to 8.1% at the high end," by 2050 although with "very large regional differences" including "a contraction of the highly productive marginal sea ice biome by 42% in the Northern Hemisphere and 17% in the Southern Hemisphere."[44] A more recent multi-model study estimated that primary production would decline by 2-20% by 2100 A.D.[17] Despite substantial variation in both the magnitude and spatial pattern of change, the majority of published studies predict that phytoplankton biomass and/or primary production will decline over the next century.[16][45][46][47][48][49][50][51][52]

Temporal Distribution Of phytoplankton :
Temporal distribution of phytoplankton refers to temporary occurrence of abnormal place (not in natural habitat).Such as,of rainy season or during flooding water bears plankton on land from any lake. After the season flooding plankton come back to natural habitat with water.Sometimes, when water dry up then plankton die at the place due to harash environmental condition. This temporary distribution is called temporal distribution.

Phytoplankton are a key food item in both aquaculture and mariculture. Both utilize phytoplankton as food for the animals being farmed. In mariculture, the phytoplankton is naturally occurring and is introduced into enclosures with the normal circulation of seawater. In aquaculture, phytoplankton must be obtained and introduced directly. The plankton can either be collected from a body of water or cultured, though the former method is seldom used. Phytoplankton is used as a foodstock for the production of rotifers,[55] which are in turn used to feed other organisms. Phytoplankton is also used to feed many varieties of aquacultured molluscs, including pearloysters and giant clams. A 2018 study estimated the nutritional value of natural phytoplankton in terms of carbohydrate, protein and lipid across the world ocean using ocean-colour data from satellites,[56] and found the calorific value of phytoplankton to vary considerably across different oceanic regions and between different time of the year.[56][57]

The production of phytoplankton under artificial conditions is itself a form of aquaculture. Phytoplankton is cultured for a variety of purposes, including foodstock for other aquacultured organisms,[55] a nutritional supplement for captive invertebrates in aquaria. Culture sizes range from small-scale laboratory cultures of less than 1L to several tens of thousands of liters for commercial aquaculture.[55] Regardless of the size of the culture, certain conditions must be provided for efficient growth of plankton. The majority of cultured plankton is marine, and seawater of a specific gravity of 1.010 to 1.026 may be used as a culture medium. This water must be sterilized, usually by either high temperatures in an autoclave or by exposure to ultraviolet radiation, to prevent biologicalcontamination of the culture. Various fertilizers are added to the culture medium to facilitate the growth of plankton. A culture must be aerated or agitated in some way to keep plankton suspended, as well as to provide dissolved carbon dioxide for photosynthesis. In addition to constant aeration, most cultures are manually mixed or stirred on a regular basis. Light must be provided for the growth of phytoplankton. The colour temperature of illumination should be approximately 6,500 K, but values from 4,000 K to upwards of 20,000 K have been used successfully. The duration of light exposure should be approximately 16 hours daily; this is the most efficient artificial day length.[55]

^Redfield, Alfred C. (1934). "On the Proportions of Organic Derivatives in Sea Water and their Relation to the Composition of Plankton". In Johnstone, James; Daniel, Richard Jellicoe (eds.). James Johnstone Memorial Volume. Liverpool: University Press of Liverpool. pp. 176–92. OCLC13993674.